Loading In Different Directions Research Articles

Seismic loading assessment of a novel structural column testing equipment

In experimental investigation on seismic performance of structural columns, it is particularly important that the loading device can reproduce a structure’s gravity load and apply a lateral seismic load at the same time, and both should be decoupled. Based on this concept, a two-dimensional multi-usage structural testing equipment (ZJU-MUST) has been developed with the following features: (1) the horizontal loading is ensured perpendicular to the vertical loading, and the loads in different directions are decoupled; (2) horizontal and vertical forces applied to testing specimen can be directly measured without the need to correct the secondary effects due to friction or vertical loading; (3) it is more reliable and suitable for cyclic loading under variable vertical forces. A 2600 mm high steel tubular column was designed for both cyclic loading tests and pseudo-dynamic tests. From the column test, the control system of ZJU-MUST as well as its performance in real-time data transmission and calculation can be verified.

A phase-field model for study of ferroelastic deformation behavior in yttria stabilized zirconia

A modified phase-field model coupled with linear elasticity is formulated to study the effect of ferroelastic domain switching on the deformation behavior of tetragonal-prime yttria-stabilized zirconia. Simulations are performed under uniaxial tension and compression using realistic domain microstructures. This work provides new insights into the mechanism of ferroelastic deformation by studying the evolution of domains under different loading directions and strain rates. The model predicts realistic stress-strain curves consisting of stress-plateaus with accurate domain switching behavior without setting a switching criterion based on a critical stress for nucleation of new domains. The results reveal that the origin of coercive stress lies in the balance between the energy absorbed by the domain switching process and the externally applied energy. Loading in different directions but parallel to the spontaneous strain results in different levels of coercive stress as domain switching absorbs different amounts of energy. For the same reason when the strain-rate increases, the coercive stress also increases. This work establishes the relation between the coercive stress and microstructural changes during ferroelastic domain switching.

Seismic performance of joints of prefabricated corrugated steel utility tunnels Part(I)–Experimental analysis

This paper presents the seismic performance of a corrugated steel plate utility tunnel, based on an engineering prototype. The research combines quasi-static testing and numerical simulation to investigate the behavior of the structure under cyclic loads in different directions. Specifically, six loading scenarios were considered: the quasi-static test was conducted for transverse tension and compression, transverse bending and shear, vertical shear test (Conditions (1–3)), while numerical simulations were performed for longitudinal tension and compression, transverse shear, and vertical bending shear test (Condition (4–6)) in Part(II). The results reveal comprehensive hysteresis curves for the plate under diverse loading directions, with an extended yield platform section that underscores its significant plastic deformation capacity. However, the “pinch” phenomenon of the hysteresis curve is obvious. The existence of rounded corners not only makes the hysteresis curve of the plate asymmetrical but also makes a great difference to the bearing capacity of the structure in the direction of positive and negative loading. The component exhibits superior bearing capacity and stiffness along the longitudinal direction compared to other orientations. Additionally, the structure demonstrates remarkable energy dissipation capabilities because of the inherent “accordion effect” of the corrugated steel plate. Moreover, the maximum energy dissipation coefficient in three directions is more than 1.0, illustrating its excellent energy dissipation capacity. The results provided valuable insight into the seismic performance of joints and contributed to the safe design of prefabricated corrugated steel utility tunnels.

Modeling the shear behavior of spunbond nonwoven fabrics using the finite element method

Nonwovens are among the most commonly used textiles in various industries. Therefore, the study of their behavior under different stresses has always been of interest to researchers. In this paper, four nonwoven fabrics with weights of 30, 70, 90 and 160 g/m2 were selected. First, each fabric was subjected to a tensile load in different directions. Subsequently based on the results obtained, the parameters related to the elastic and plastic properties, as well as the progressive damage in each direction, were determined. Next, a model was created to simulate the shear stress on fabrics using Finite Element Method (FEM). On the other hand, it was assumed that the fabrics cab be made up of one, two or three-layer structures, with each layer being defined by the tensile behavior of the fabric in a specific direction. The comparison between the experimental results and the FEM output revealed that the single-layer models have relatively low accuracy regardless of the fabric weight. For fabrics weighing less than 80 g/m2, the three-layer structure can achieve the relative error of 7% and lower by combining the tensile properties in the longitudinal and diagonal directions. Moreover, even for the fabrics that are heavier, the three-layer structure can be used by combining the tensile properties in the longitudinal, transverse and diagonal directions. But in this case, it leads to the relative error of 13% and lower.

Investigation of transportation infrastructure elements on the example of spherical bridge bearing

Transportation infrastructure consists mainly of critical elements. They are subjected to a large set of requirements for strength, rigidity, reliability. The article considered deformation behavior of spherical bridge bearing at different introduction depth parameters of sliding layer. The influence of contact surface treatment on the character of contact parameters distribution is studied. Earlier the polymers and composites behavior was viewed as an elastic-plastic material. However, for predicting their life-cycle it is necessary to consider them as viscoelastic. The article compared the parameters obtained by modeling elastic-plastic and viscoelastic materials behavior. The influence of sliding layer thickness on the deformation structure behavior was also discussed. It is revealed that sliding layer modeling as an elastic-plastic body is sufficient for numerical calculations on determination of strength characteristics. However, it is necessary to consider the sliding layer as a viscoelastic/viscous-elasticplastic material to design the life cycle of the structure taking into account rheology, thermomechanics and cyclic loads in different directions.

Clear-water scour at monopile foundations subjected to cyclic lateral loads in different directions

Monopile foundations have been widely used to support offshore wind turbines in shallow waters. Current-induced local scour at monopile foundations, as a universal problem threatening the structure safety and the operational efficiency of the turbines, has been extensively studied in recent decades by flume experiments and numerical models. Recent studies reported that the scour process around monopile foundations is affected by cyclic lateral loads induced by waves, currents, and winds. However, the scour mechanism around monopile foundations subjected to cyclic lateral loads in different directions remains unclear, necessitating further investigation. This paper presents an experimental study investigating the clear-water scour characteristics around monopile foundations under cyclic lateral loads applied parallel and perpendicular to the flow direction at a relatively low flow intensity. The experimental results reveal that when the amplitudes of the cyclic lateral loads exceed 4% of the monopile diameter at the monopile’s top, the equilibrium scour depths at monopile foundations subjected to cyclic lateral loads perpendicular to the flow direction are generally larger than those under cyclic lateral loads parallel to the flow direction. Sour holes extent more significantly in the direction of cyclic lateral loads rather than the unload direction, and the slope angles in the load directions are gentler than those in the unload directions. Furthermore, based on the experimental data, an empirical equation is proposed to predict the current-induced equilibrium scour depth at cyclically vibrating monopile foundations in different directions.

Biomechanical comparison of different internal fixation devices for transversely unstable Mason type II radial head fractures.

Background: The integrity of the radial head is critical to maintaining elbow joint stability. For radial head fractures requiring surgical treatment, headless compression cannulated screw fixation is a less invasive scheme that has fewer complications. The aim of this study was to compare the mechanical stability of different fixation devices, including headless compression cannulated screws and mini-T-plates, for the fixation of transversely unstable radial head fractures. Methods: Forty identical synthetic radius bones were used to construct transverse unstable radial head fracture models. Parallel, cross, and tripod headless compression cannulated screw fixation and mini-T plate fixation were applied. The structural stiffness of each group was compared by static shear loading. Afterward, cyclic loading was performed in each of the three directions of the radial head, and the shear stability of each group was compared by calculating the maximum radial head displacement at the end of the cycle. Findings: The mini-T plate group had the lowest structural stiffness (51.8 ± 7.7N/mm) and the highest relative displacement of the radial head after cyclic loading (p < 0.05). The tripod headless compression cannulated screw group had the highest structural stiffness among all screw groups (p < 0.05). However, there was no significant difference in the relative displacement of the radial head between the screw groups after cyclic loading in different directions (p > 0.05). Interpretation: In conclusion, the biomechanical stability of the mini-T plate for fixation of transverse unstable radial head fractures is lower than that of headless compression cannulated screws. Tripod fixation provides more stable fixation than parallel and cross fixation with headless compression cannulated screws for the treatment of transversely unstable radial head fractures.

A constitutive model for the gravelly soil-structure interface considering particle breakage and fabric change

The isolated foundation with cushions is gaining popularity as a viable option for building bridges in active seismic zones due to its exceptional seismic isolation performance. However, the efficacy of this foundation relies heavily on the interactions within the cushion layer and between the caisson foundation and the cushion layer. The cushion layer, composed of 0.5 m thick crushed aggregate layer and 2.5 m thick pebble gravel, is susceptible to particle breakage and fabric change, which can significantly impact the overall behavior of the foundation. To better characterize the mechanical behavior of the cushion layer and the interface between aggregates and the structure, a new elastoplastic constitutive model is proposed in this study. The current model is built based on an existing constitutive model, Saberi’s model (Model-S). Two parameters are introduced, including a particle breakage coefficient, B10, calculated by total plastic work, and a fabric-dilatancy variable, z, to determine the interfacial dilatancy variation. The current model consists of 13 parameters in total. Comparison evident that the current interfacial constitutive model can better simulate the change of the physical state and asymmetrical response in the stress-displacement relationship due to symmetrical loading in different directions.

Experimental study and mechanism analysis of out-of-plane seismic performance of reinforced concrete shear walls

Compared with the in-plane seismic performance, the out-of-plane seismic performance of reinforced concrete shear walls is weak and usually neglected, which leads to an inadequate study of the out-of-plane damage mechanism of shear walls and a lack of clear protective measures. In order to compare the similarities and differences in seismic performance of reinforced concrete shear walls when subjected to in-plane and out-of-plane loads in different directions and to clarify the key influencing factors, low cyclic loading tests were carried out on typical shear wall specimens in both in-plane and out-of-plane directions. The moment-curvature simulations of shear wall sections in both in-plane and out-of-plane directions are analyzed. The effects of parameters such as axial pressure ratio, wall thickness, height to width ratio and concrete grade on in-plane and out-of-plane seismic performance were analyzed at the member level in combination with finite element variable parameter analysis; at the structural system level, the time history analysis of 2 frame shear wall structures for single seismic action and main-aftershock sequence is established, and the structural damage is evaluated through the maximum story drift and rotation. The results reveal that the out-of-plane seismic performance of shear walls is significantly weaker than their in-plane seismic performance, with a difference of 1/20∼1/15 times in bearing capacity, where wall thickness and aspect ratio are the main parameters affecting in-plane and out-of-plane seismic performance; when the shear walls in the structure are subjected to seismic action in the out-of-plane direction, their out-of-plane direction will undergo large deformation and damage will occur easily, especially in the Single directional wall with less structure. The out-of-plane nonlinear analysis of the cross-section can be performed more accurately and quickly by using the new principal structure model proposed in this manuscript and some traditional principal structures. In the seismic design of shear walls, both in-plane and out-of-plane seismic performance should be ensured, and the wall thickness and height to width ratio of shear walls should be reasonably controlled.

Experiment on the impact response of aluminum alloy wood core sandwich composites

In this work, a protective structure with 2A12T4 aluminum alloy as the panel material and plywood as the core layer was designed. Penetration experiments were performed by firing multiple projectiles from a light gas gun. The impact behavior, damage mode, absorbed energy, and residual strength of the interlayer after impact were studied. The dynamic response and the failure of the interlayer were analyzed. Disbonding, fiber fracture, buckling, shear, and core fracture between the metal layer and the composite layer of the front panel were observed. The impact resistance of the sandwich plate was also studied. Based on the results of the experiments and numerical simulations, failure determination of the plywood core layer was achieved using the Hashin criterion, and a finite element model was established using ABAQUS software. High-speed impact testing was performed with a Hopkinson pressure bar. The stress–strain relationship under a high dynamic strain rate is given here, and the energy absorption efficiency under loading in different directions was analyzed. Finite element analysis of the representative volume elements in the wood microstructure was also carried out. The results reported here can be used to guide optimal design of sandwich structures suitable for use under high-speed impact conditions.

A combined experimental and crystal plasticity study of grain size effects in magnesium alloys

This work presents a method to incorporate the micro Hall-Petch equation into the crystal plasticity finite element (CPFE) framework accounting for the microstructural features to understand the coupling between grain size, texture, and loading direction in magnesium alloys. The effect of grain size and texture is accounted for by modifying the slip resistances of individual basal and prismatic systems based on the micro Hall-Petch equation. The modification based on the micro Hall-Petch equation endows every slip system at each microstructural point with a slip system-level grain size and maximum compatibility factor, which are in turn used to modify the slip resistance. While the slip-system level grain size is a measure of the grain size, the maximum compatibility factor encodes the effect of the grain boundary on the slip system resistance modification and is computed based on the Luster-Morris factor. The model is calibrated using experimental stress-strain curves of Mg-4Al samples with three different grain sizes from which the Hall-Petch coefficients are extracted and compared with Hall-Petch coefficients predicted using original parameters from previous work. The predictability of the model is then evaluated for a Mg-4Al sample with different texture and three grain sizes subjected to loading in different directions. The calibrated parameters are then used for some parametric studies to investigate the variation of Hall-Petch slope for different degrees of simulated spread in basal texture, variation of Hall-Petch slope with loading direction relative to basal poles for a microstructure with strong basal texture, and variation of yield strength with change in grain morphology. The proposed approach to incorporate the micro Hall-Petch equation into the CPFE framework provides a foundation to quantitatively model more complicated scenarios of coupling between grain size, texture and loading direction in the plasticity of Mg alloys.

Three-point bending performances of integral-forming aluminum foam sandwich

In the course of service, integral-forming aluminum foam sandwich (IFAFS) needed to bear three-point bending loads in different directions, however, its deformation mechanism and failure modes were still unclear. In this work, three-point bending performances of IFAFS under flatwise and edgewise bending conditions were investigated by experiment, in-situ micro X-ray tomography and digital volume correlation (DVC) calculation. The results showed that three-point bending performance was more stable under edgewise bending condition, and with the decrease of span length IFAFS presented three different failure modes of oblique core shear, asymmetric and symmetrical surface fracture. In addition, porosity mutation was a significant reason for crack initiation, and optimizing pore homogeneity was important to improve the performance and predictability of failure location. Different strengthening effect of sandwich structure anisotropy and different internal deformation evolutions caused by internal strain vortex were two main reasons which lead to performance difference of IFAFS with different solid panel directions. Connection of pre-existing micropores with dimple-like micropores generated during deformation process leads to the failure of IFAFS. The key factors to further optimize three-point bending performance and predictability of IFAFS was to homogenize the pore distribution of IFAFS.

Experimental and numerical investigation of blast loads induced by moving charge explosion

With the development of high-speed weapons, moving charge explosions frequently occur in industry and military activities, which will lead to significant damage to structures. In order to investigate the blast loads induced by moving charge explosion, explosion experiments are carried out. The pressure curves and blast load parameters are analyzed. Results indicate that the blast load distribution is directional in moving charge explosion, and the blast load parameters are influenced by distance and direction. Numerical simulation investigation is conducted to further study the effect of charge shape and velocity on blast loads induced by moving charge explosion. The numerical model is developed and verified with experiment data, which indicates that the numerical method is sufficiently accurate for moving charge explosion investigation. The numerical study characterizes the influence of charge shape and charge velocity on blast loads in different directions. The shape factors of cylindrical charge and the velocity factors of 580 m/s, 700 m/s, 900 m/s and 1200 m/s in moving charge explosion are analyzed. The results indicate that the charge shape effect must be considered in the near-field and the charge velocity effect must be considered in different directions, especially in directions with angles less than 90°. This research will contribute to combatant power evaluation, structural engineering and structural design.

Exploring three-point-bending fracture toughness of thick diamond films from different directions

In this study, the effect of defects on fracture toughness in different directions was investigated. Two diamond films with a diameter of 122 mm and as-deposited thicknesses of 2.2 and 1.5 mm, respectively, were deposited by DC arc plasma jet chemical vapor deposition. To accurately obtain the fracture toughness, the films were ground and polished to 1.6 and 0.8 mm, respectively. The results indicate that many defects, including pores, are introduced into the films during the growth process, particularly on the side close to the growth surface in thicker film. The size of pores reaches micrometres, which affects the fracture toughness under loading in different directions. Due to the minimum grain size, both films exhibit a maximum toughness of 8.2 and 10.0 MPa·m1/2, respectively, with growth-surface cracks. For the thinner sample, the maximum value is followed by that of the edge-surface cracks. As the grain size of the edge surface falls between that of the growth surface and that of the nucleation surface, the results indicate that fracture toughness is affected by grain size. However, the number of pores near the growth side increases when the thickness exceeds 0.8 mm. Pores reduce the toughness, resulting in the minimum fracture toughness (6 MPa·m1/2) of the thicker diamond film with edge-surface laser cracks. The sample with an edge-surface sharp pre-crack has a similar fracture toughness of 5.6 MPa·m1/2. This study provides guidance for selecting the applied load direction.

Sensitivity Analysis of Factors Affecting the Bearing Capacity of Suction Bucket Foundation in Soft Clay

A suction bucket is the foundation for the development of offshore wind power technology in the deep sea, and its stability is crucial to the superstructure of the wind power generation system. Combined with soft clay soil strata along the Chinese coast, the bearing capacity of suction bucket foundations was studied using a numerical model. Sensitivity factors such as soil strength with random space distribution, dimensions of foundation, wind and wave loads in different directions, and cycle times were considered. The results show that the normalized foundation bearing capacity coefficient increases with the increase of the foundation length–diameter ratio. When the foundation length–diameter ratio is less than 1.0, the foundation bearing capacity coefficient is more sensitive to the soil non-uniformity coefficient than the length–diameter ratio. When the length–diameter ratio of the suction bucket is large enough, the influence of the soil non-uniformity coefficient on the bearing capacity of the suction bucket foundation gradually diminishes. When the direction of wind and wave loads is 15°, the bearing capacity of the suction bucket foundation is the weakest. Under the cyclic loads, the shallow soil strength weakens faster in the initial stage and the attenuation rate of soil strength slows down in the latter stage.

Behavior of woven fabric composite under tensile loads in different directions using acoustic emission

The woven fabric composites were used in different industries for their special specification. This study aimed to address failure mechanisms in single-layer woven fabrics. The acoustic emission (AE) technique and wavelet transform were used for composite structural health monitoring and failure rate evaluation. From a mechanical study viewpoint, the load-displacement behavior of plain-woven glass composite was examined under tension in the principal directions (0 and 90°) and off-axis (30, 45, and 60°). The results indicated that off-axis samples are deformed and curled due to the slippage and rotation of warp and weft yarns. The mechanical measurements were synchronized with the AE data in an acousto-mechanical study. The load-displacement behavior of samples was zoned out with two criteria: frequency and energy. Eventually, three failure modes were identified: matrix damage, interface damage, and fiber breakage. The results showed that events with a frequency above 400 kHz at different angles could be attributed to fiber breakage. Also, the applied force angle effectively affects the type of fiber failure (tensile and shear failure). It was found that in addition to tensile failure, shear failure also increases sharply by increasing the angle between the main directions. So that the maximum number of shear fiber failures occurred at the angle of 45° between the main directions. On the off-axis, the number of fibers exposed to the load also increased, increasing the number of breakages.

Dynamic response and time-variant reliability analysis of an eight-rod shock isolator

The operation of a warship is commonly affected by shock loads in different directions during sailing in a rough sea, which can decrease the precision of the shipboard equipment. To improve the shock resistance performance of the shipboard equipment, an isolator is usually installed to isolate it from the vibration of the ship deck. The paper proposes a method for dynamic response and time-variant reliability analysis of an eight-rod shock isolator (ERSI). ERSI has a novel symmetrical structure, which can improve the utilization of the isolation rods compared with the classical parallel mechanism. The isolator is modeled using Denavit-Hartenberg (D-H) convention and screw theory. Then, Duhamel integral is employed to derive the dynamic response to the isolator after decoupling the governing equation using the modal analysis method. Considering impacts of uncertain factors, this paper also presents a practical method for time-variant reliability analysis of ERSI. Finally, a discussion of the practical example of this method along with a detailed analysis to evaluate the efficiency of the proposed method is presented.

Study on the effects of H on the plastic deformation behavior of grain boundaries in nickel by MD simulation

It is generally believed that the influence of hydrogen on plastic deformation of grain boundaries should be considered when analyzing hydrogen-induced intergranular fracture in polycrystalline metals. In this paper, the equilibrated H distribution around GBs was firstly investigated by employing the grand canonical Monte Carlo method. Then, MD simulations were performed to study the plastic response of GBs under uniaxial tensile loads in different directions, with various bulk H concentrations considered. The results indicate that the influence of H on dislocation nucleation from GB depends on both tensile directions and characteristics of GB structures. Specifically, two dislocation nucleation mechanisms, called dislocation dissociation nucleation (DDN) and heterogeneous dislocation nucleation (HDN), are identified. Careful analyses show that H segregation can increase the energy barrier of DDN, which results in H-inhibited dislocation nucleation. In contrast, the HDN mechanism involves H-enhanced or H-insensitive dislocation nucleation, which mainly depends on the influence of H on GB stress.

A new anisotropic poroelasticity model to describe damage accumulation during cyclic triaxial loading of rock

SUMMARY Crustal rocks undergo repeated cycles of stress over time. In complex tectonic environments where stresses may evolve both spatially and temporally, such as volcanoes or active fault zones, these rocks may experience not only cyclic loading and unloading, but also rotation and/or reorientation of stresses. In such situations, any resulting crack distributions form sequentially and may therefore be highly anisotropic. Thus, the tectonic history of the crust as recorded in deformed rocks may include evidence for complex stress paths, encompassing different magnitudes and orientations. Despite this, the ways in which variations in principal stresses influence the evolution of anisotropic crack distributions remain poorly constrained. In this work, we build on the previous non-linear anisotropic damage rheology model by presenting a newly developed poroelastic rheological model which accounts for both coupled anisotropic damage and porosity evolution. The new model shares the main features of previously developed anisotropic damage and scalar poroelastic damage models, including the ability to simulate the entire yield curve through a single formulation. In the new model, the yield condition is defined in terms of invariants of the strain tensor, and so the new formulation operates with directional yield conditions (different values for each principal direction) depending on the damage tensor and triaxial loading conditions. This allows us to discern evolving yield conditions for each principal stress direction and fit the measured amounts of accumulated damage from previous loading cycles. Coupling between anisotropic damage and anisotropic compaction along with the damage-dependent yield condition produces a reasonable fit to the experimentally obtained stress–strain curves. Furthermore, the simulated time-dependent cumulative damage is well correlated with experimentally observed acoustic emissions during cyclic loading in different directions. As such, we are able to recreate many of the features of the experimentally observed directional 3-D Kaiser ‘damage memory’ effect.

Length Influences on Lateral Performance of Barrette from Three-Dimensional Finite Element Analysis

ABSTRACT The performance of a single barrette subjected to lateral load applied at its top is presented in this paper using three-dimensional finite element analyses based on Midas GTS program. Nonlinear behaviors of the barrettes buried in clayey and sandy soils were monitored using Mohr-Coulomb soil model. Performances of the barrettes with lateral loads applied in both longitudinal and transverse directions were examined. Displacements of the barrettes affected by stiffness and strength of the soils were obtained and normalized with the nominal length of the barrette. The criteria for long and rigid barrettes with loads in different directions were suggested. For the barrettes with loads in the transverse direction, the conventional analytical solution suggested by Chang for a single pile was found applicable to the predictions. In such case, the equivalent diameter calculated from moment of inertia of the barrette was found more adequate to be used in the analytical solution. Results of this study can help the engineers to understand more about the barrette performance under lateral loads.